Merge pull request #5008 from kobotoolbox/fix-timeout-in-project-view…

…-new-class

Fix project view table timeout

kobo/apps/project_views/views.py

@@ -16,6 +16,7 @@
 )
 from kpi.mixins.object_permission import ObjectPermissionViewSetMixin
 from kpi.models import Asset, ProjectViewExportTask
+from kpi.paginators import FastAssetPagination
 from kpi.permissions import IsAuthenticated
 from kpi.serializers.v2.asset import AssetMetadataListSerializer
 from kpi.serializers.v2.user import UserListSerializer
@@ -52,6 +53,7 @@ def get_queryset(self, *args, **kwargs):
         detail=True,
         methods=['GET'],
         filter_backends=[SearchFilter, AssetOrderingFilter],
+        pagination_class=FastAssetPagination,
     )
     def assets(self, request, uid):
         if not user_has_view_perms(request.user, uid):

kpi/paginators.py

@@ -121,6 +121,21 @@ class DataPagination(LimitOffsetPagination):
     offset_query_param = 'start'
     max_limit = settings.SUBMISSION_LIST_LIMIT
 
+
+class FastAssetPagination(Paginated):
+    """
+    Pagination class optimized for faster counting for DISTINCT queries on large tables.
+
+    This class overrides the get_count() method to only look at the primary key field, avoiding expensive DISTINCTs
+    comparing several fields. This may not work for queries with lots of joins, especially with one-to-many or
+    many-to-many type relationships.
+    """
+
+    def get_count(self, queryset):
+        if queryset.query.distinct:
+            return queryset.only('pk').count()
+        return super().get_count(queryset)
+
 
 class TinyPaginated(PageNumberPagination):
     """